1. Field of the Invention
The present invention relates to a wheel assembly and, more particularly, to a wheel assembly containing a wheel and a tire of which an internal air pressure is adjustable and a wheel condition determining apparatus that can detect an abnormality in such a wheel assembly.
2. Description of the Related Art
Generally, an air compressed at a predetermined pressure is charged in a tire so as to reduce vibrations during running of a vehicle. The tire is hermetically sealed so that the predetermined pressure is maintained inside the tire. However, the air inside the tire may slowly leak outside over time, depending on a weight of the vehicle, a material of the tire or a running condition of the vehicle, which is referred to as a natural air leak phenomenon. In order to suppress an influence of the natural air leak phenomenon, there have been suggested various devices. For example, the air pressure inside the tire is maintained by a technique such as disclosed in Japanese Laid-Open Patent Application No. 9-508870 that compensates for a drop in the tire pressure using a centrifugal force generated during rotations of the tire.
Although, the above-mentioned technique that compensates for a drop in the tire pressure using a centrifugal force generated during rotations of the tire is excellent in that a drop in an air pressure inside a tire can be semi-automatically compensated for, there may be a case in which it is difficult to adjust an air pressure inside the tire accurately to an optimum state. For example, an excessive centrifugal force may be generated depending on a rotational condition of a wheel, which results in an excessive air charged into the tire.